This seems to be your opinion as it is not my experience. My beta expired with iOS 6 and it was incredibly easy to get to a computer and simply downgrade back to iOS 5. It was not hard. The hardest part was that the beta expired while I wasn't home and had to wait to get home before I had my phone again. I survived.
I was mainly referring to people who downloaded a file off the interwebs somewhere and installed it, without having a registered UDID.
Granted, something like that happening is slim, but it has happened to a few people here trying to downgrade after installing iOS 7. Whether it was due to user error or some unknown bug, I don't know. Either way, rumors like what the OP is asking about are not something I am worried about. For all we know, the rumor was started on Twitter or some other social network, as a means for scammers to get more money selling UDID's.